diff --git a/wp-includes/sitemaps/class-wp-sitemaps-registry.php b/wp-includes/sitemaps/class-wp-sitemaps-registry.php
index 5cb2e2fa45..6edf1dfe5c 100644
--- a/wp-includes/sitemaps/class-wp-sitemaps-registry.php
+++ b/wp-includes/sitemaps/class-wp-sitemaps-registry.php
@@ -65,7 +65,7 @@ class WP_Sitemaps_Registry {
 	 * @return WP_Sitemaps_Provider|null Sitemap provider if it exists, null otherwise.
 	 */
 	public function get_provider( $name ) {
-		if ( ! isset( $this->providers[ $name ] ) ) {
+		if ( ! is_string( $name ) || ! isset( $this->providers[ $name ] ) ) {
 			return null;
 		}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 6f3c67597d..20edb79d9b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-alpha-53837';
+$wp_version = '6.1-alpha-53838';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.